Question: If $a + b + c = -1$ and $x + y + z = 8$, what is $9c - 9z - 9y - 9x + 9b + 9a$ ?
$= 9a + 9b + 9c - 9x - 9y - 9z$ $= (9) \cdot (a + b + c) + (-9) \cdot (x + y + z)$ $= (9) \cdot (-1) + (-9) \cdot (8)$ $= -9 - 72$ $= -81$